obama and castro with the keynote address. here on c-span2, it's booktv all day everyday throughout the convention with highlights of non-fiction authors and books from the past year. and on c-span 3, also throughout the convention, 24 hours of american history tv. with lectures, oral history, and a look at historical american sites and art -- artifacts. >>> from the american museum of natural history in new york city. astrophysic talks about the history and future of nasa. and the u.s. space program. he argues that the exploration of space benefits more thans more than they might think. it's a little over two hours. good evening, everyone, and welcome. thank you for your patience. my name is suzanne morris, i'm the senior manager of public programs. we are thrilled to have you all here tonight, so give yourselves a round of applause. [applause] the american museum of natural history has been home to some of the country's greatest thinkers. scientists and citizens who have changed the way we understand scientific and natural p